Although the concept is obscure outside the discipline of structurally confined rubber spring design, and limited in understanding within the discipline, general applications of such rubber springs have been attempted in the past. Usually, the outer structure is hollow cylindrical, and an inefficient use of at least the lower regions of the internally located rubber results. The springs are not very spring rate tunable when the wall has a purely cylindrical configuration, and the rubber has undefined or unstable coefficient(s) of friction with the support wall, as increased interfacing occurs.
Additionally, durability is a problem, due to abrasion at the contact stick and slip surfaces between the outside of the rubber spring and the inside of the support structure. Other prior art, regarding column stability, teaches locating a hole in the cylindrical rubber spring column, and inserting a structural post whose height does not exceed the maximum deflected height of the spring. This gives column stability, but is not as efficient, nor as durable, as the presently disclosed invention, and is non-tunable.
Examples of such springs are illustrated by U.S. Pat. Nos. 3,262,985 and 3,037,764.